The document, WO 2006/067252 A1 makes known an expanding device for expanding a self-expandable foldable display, the display having two panels connected to one another by their lateral edges. The mentioned expanding device comprises a plate divided by a first hinge into first and second plate portions, at least one of which is connected to at least one panel of the display. An elastic tensile element is provided for pulling the first and second plate portions towards each other to fold the plate around said first hinge from a flat folded position to an angled working position. The plate comprises a limiting member, which has a connection edge connected by a second hinge to the first plate portion and a free edge, which, when the plate is in said angled working position, is in contact with the second plate portion in order to limit the folding of the plate to an angled working position. However, in this expanding device, the second hinge is parallel to the first hinge and the panels of the display are not flat panels, but in the expanded position, they are pushed from within outwards by the expanding device and adopt a bulged convex arrangement.
The document, WO 2010/018272 A1 describes an expanding device comprising two or more plates made from cardboard sheet or another similar material cooperating with one or more elastic tensile elements, which may be applied to maintain upright a display formed by one single flat panel or to expand a self-expandable foldable display made of three or more cardboard panels or other similar material connected by their lateral edges from a collapsed position to an expanded position capable of being maintained upright. However, this expanding device, when it is used with the display formed by one single flat panel, has the drawback that the one or plurality of elastic tensile elements and its hook elements are exposed and are visible in the working position and when it is used with the self-expandable foldable display made of three or more panels connected by their lateral edges, it has the drawback that the plates of the expanding device are not superimposed upon interior surfaces of the flat panels of the display and do not act as reinforcing plates for these flat panels of the display.